Tunable SIW bandpass filter-combined microstrip antenna based on liquid crystals

In this paper, the design and experimental characterization of a novel tunable Substrate Integrated Waveguide (SIW) filter and tunable microstrip patch antenna in multilayer technology based on liquid crystals (LCs) are presented. To realize the concept, the SIW filter and patch antenna are combined directly coupled by T-slot at the middle of the common ground plane. Due to their flexibility as a liquid dielectric and because of their anisotropic characteristics, they have been used widely in telecommunication devises, display technologies, and RF and microwave devices. The dielectric proprieties of LCs are controlled through the strength of the bias voltage of 15 V, a return loss (S11) better than −35 dB with a global bandwidth of around 425 MHz (18%) and a frequency agility of 13.75%, are demonstrated. A good agreement is noticed between the simulated and the measured data.